[Code Style] com_users frontend

This fixes all the code style issues on `com_users` frontend.

This PR requires 2 tests as I've been forced to modify code:

https://github.com/phproberto/joomla-cms/compare/joomla:staging...phproberto:users-frontend?expand=1#diff-cd009ab48167c723aade8808e600cb79L166

## Tests required

We need to check:

* Users are able to save their profile in **frontend** and they are redirected correctly 
* On errors when editing the profile form the users are redirected back to the profile edit form